Selector switch for load tap-changers of regulating transformers



y 1959 A. BLEIBTREU ETAL 3,445,511

SELECTOR SWITCH FOR LOAD TAP-CHANGERS OF REGULATIN G;TRANSFORMERS FiledJuly 12, 1967 Sheet of 5 um k v, WWW k W W W y 20, 1969 A. BLEIBTREUETAL 3,445,611 I SELECTOR SWITCH FOR LOAD TAP-CHANGERS F REGULATINGTRANSFORMERS Sheet Filed July 12, 1967 r //VVE/V70/PS (wumm mm um M. mm

May 20; 1969 A. BLEIBTREU ETAL 3,445,611

SELECTOR SWITCH FOR LOAD TAP-CHANGERS OF REGULATING TRANSFORMERS SheetFiled July 12, 1967 May 20, 1969 A. BLEIBTREU ETAL 3,445,611

SELECTOR SWITCH FOR LOAD TAP-CHANGERS OF REGULATING TRANSFORMERS FiledJuly 12, 196'? Sheet 4 of 5 (Wm/m WM UM A. XMM

M WWW WW May 20,1969 A. BLElBTREU ETAL-Q 3,445,611

' SELECTOR SWITCH FOR LOAD TAP-CHANGERS OF REGULATING TRANSFORMERS FiledJuly 12, 1967 Sheet 5 015 3 llil 1 7 r vI.

United States Patent O US. Cl. 200-11 Claims ABSTRACT OF THE DISCLOSUREDisclosed below is a selector switch for load tapchangers of regulatingtransformers of the type including a plurality of fixed contactsarranged in two coaxial circular patterns each situated in one of twodifferent planes. One of the two aforementioned circular patterns offixed contacts is intended to be conductively connected to the evennumbered taps of a transformer winding and the other of the twoaforementioned patterns of fixed contacts is intended to be conductivelyconnected to the odd numbers taps of a transformer winding. In such anarrangement the circular pitch is the distance from the center of onecontact to the center of the next consecutive contact measured on thecircle along which the contacts are arranged, or which may be drawnthrough the centers thereof. The structure disclosed includes means foroperating a pair of contact arms or contact bridges engaging the fixedcontacts in steps equal to half the circular pitch of the contacts andadditional slide contacts which establish a conductive connectionbetween the aforementioned pair of contact arms or contact bridges whenthe same are in registry positions. As a result of these features allcontacts pertaining to one phase of a transfer switch and operativelyrelated to the selector switch are maintained at the same potential,except during tap-changing operations of the transfer switch.

BACKGROUND OF INVENTION This invention relates to selector switches ofthe kind disclosed in US. Patent 3,176,089 to A. Bleibtreu at al., LoadTap Changers for Transformers, Mar. 30, 1965; US. Patent 3,233,049 to A.Bleibtreu, Integral Selector Switch and Transfer Switch Unit for TappedRegulating Transformers, Feb. 1, 1966; and US. Patent 3,250,864 to A.Bleibtreu et al., Regulating Transformers Having a Large Number of Taps,May 10, 1966.

Such selector switches are intended to be operatively related to both atapped transformer winding and a transfer switch. The transfer switch isinterposed between a tap of a tapped transformer winding which carriescurrent and other, or pre-selected, tap. In transfer switches ofregulating transformers which are operatively related to selectorswitches of the kind disclosed in the above patents there is adifference of potential between the open contacts and the closedcontacts of the transfer switch. This difference of potential is equalto the difference of potential between contiguous taps of the tappedregulating winding of the transformer. Under certain conditions thevoltage, or difference of potential, between the open contacts and theclosed contacts of a transfer switch may be of much larger magnitudethan the voltage, or difference of potential, between contiguous taps ofa tapped transformer winding, and may reach dangerous surge voltageproportions. This fact compels to take certain precautions in the designof transfer switches to preclude breakdown of insulation therein. This,in turn, results in a substantial increase of the cost of manufacturingtransfer switches as well as an increase of the bulk of such switches.

There are a number of Ways of avoiding these drawbacks and limitations,and the present invention is concerned with one particularly desirableway of achieving this end.

A transfer switch has two limit positions. In one of these limitpositions some of the contacts of a transfer switch, i.e. the closedcontacts thereof, are connected by the intermediary of the selectorswitch to one tap of a tapped transformer winding. In that limitposition of the transfer switch some of the contacts of the transferswitch, i.e. the open contacts thereof, are connected by theintermediary of the selector switch to another tap of a tappedtransformer winding. This other tap is the pre-selected tap situatedimmediately adjacent the first mentioned tap. It is possible to providea disconnect switch for disconnecting the open contacts of the transferswitch from the tap of the tapped transformer winding which ispreselected by the position of the selector switch, and conductivelyconnecting these contacts with the closed contacts of the transferswitch, thus equalizing the potential of the open contacts of thetransfer switch and of the closed contacts thereof. The use of suchauxiliary changeover disconnect switches for the intended purpose isdisclosed and claimed in the copending patent application of Ulrich G.E. Schweitzer, filed July 5, 1967, Ser. No. 651,284, for Tap-ChangingTransformer Including a Selector Switch and a Transfer Switch assignedto the same assignee as the present invention.

In a special type of selector switches both movable contacts, or contactbridges, thereof rest on the same fixed contact when a tap-changingoperation has been performed by the transfer switch and the desired tapis connected into the load circuit. Then both movable contacts arecarrying current and this makes it possible to increase thecurrent-carrying capacity of this special type of selector switches. Insuch selector switches there are two fixed contacts for each tap of thetapped transformer winding, i.e. there are two fixed contacts which areconductively connected with the same tap and are current-sharing, thusachieving the desired increase in current-carrying capacity. In loadtap-changers including such special selector switches all the contactsof the transfer switches are at the same potential when the latter arein one of their limit positions or, in other words, in a stationarycurrentcarrying position. The above referred-to special selectorswitches are, however, subject to serious drawbacks. Since all theirdual fixed contacts of each phase must be arranged in one common plane(rather than in two parallel spaced planes) the diameter of such specialselector switches tends to be extremely large, or excessive. This is dueto the fact that a certain minimum distance or circular contact pitchmust be maintained between the contacts thereof to achieve the requireddielectric strength. In selector switches wherein the fixed contactspertaining to the same phase are arranged in two parallel spaced planesthe circular contact pitch may be much smaller than in the above specialselector switches, assuming that there are equal dielectric strength ofcontact spacing requirements in both instances.

SUMMARY OF THE INVENTION Selector switches embodying this inventioninclude a first plurality of fixed odd numbered contacts arranged in afirst circular pattern defining a first plane and a second plurality offixed even numbered contacts arranged in a second circular patterncoaxial with said first circular pattern and defining a second planespaced from and parallel to said first plane. Said first plurality offixed contacts and said second plurality of fixed contacts have apredetermined circular pitch. Selector switches embodying this inventionfurther include a pair of slip rings arranged in coaxial relation tosaid first plurality of fixed contacts and to said second plurality offixed contacts. Said pair of fixed slip rings includes a first slip ringand a second slip ring. Selector switches embodying this inventionfurther include a pair of contact bridges pivotable about the commonaxis of said first plurality of fixed contacts and said second pluralityof fixed contacts. Said pair of contact bridges include a first contactbridge and a second contact bridge. Said first contact bridge has aradially outer end permanently engaging said first slip ring and aradially inner end selectively engaging any of said first plurality offixed contacts. Said second contact bridge has a radially inner endpermanently engaging said second slip ring and a radially outer endselectively engaging any of said second plurality of fixed contacts.Selector switches embodying this invention further include a pair ofoperating means for pivoting said first contact bridge and said secondcontact bridge about said common axis of said first plurality of fixedcontact and said second plurality of fixed contacts in steps equal tohalf said circular pitch to cause said radially outer end of said firstcontact bridge to engage consecutive contacts of said first plurality ofcontacts and to cause said radially outer end of said second contactbridge to engage consecutive contacts of said second plurality ofcontacts upon having been pivoted two said steps in the same direction.Selector switches embodying this invention further include additionalcontact means establishing a conductive connection between said pair ofcontact bridges in registering positions of said pair of contactbridges.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammaticrepresentation of a single phase selector switch embodying the presentinvention combined with a conventional transfer switch of the type knownas Jansen transfer switch;

FIG. 2 is a partial top-plan view of the selector switch shown in FIG.1;

FIG. 3 is an isometric view of the selector switch shown in FIGS. 1 and2;

FIG. 4 is a vertical section of a special Geneva gear drive foroperating the selector switch of FIGS. 13, this drive includingsuper-imposed Geneva gears;

FIG. 5 is a top plan view of the drive shown in FIG. 4;

FIG. 6 is a diagram illustrating the sequence of operations of aselector switch embodying this invention and of a transfer switch whichis operatively related to it;

FIG. 7 is a vertical section of another special Geneva gear drive foroperating the selector switch of FIGS. 1-3. This drive including Genevagears which are arranged in a common plane;

FIG. 8 is a top plan view of the drive of FIG. 7;

FIG. 9 is a diagram illustrating the sequence of operations of aselector switch embodying the present invention and of a transfer switchwhen using the drive of FIGS. 7 and 8;

FIG. 10 is a top plan view of a cog-wheel drive for a selector switchembodying the present invention;

FIG. 11 is a vertical section through a drive of the kind illustrated inFIG. 10 including cog-wheels which are arranged in a common plane; and

FIG. 12 is a diagram illustrating the sequence of operations of aselector switch embodying the present invention and of a transfer switchwhen using the drive of FIGS. 10 and 11.

DESCRIPTION OF PREFERRED EMBODIMENTS In FIG. 1 reference character L hasbeen applied to generally designate a Jansen type transfer switch andreference character St has been applied to generally designate aselector switch. As explained in US. Patent 3,174,097 to A. Bleibtreu,Transfer Switch for Tap Changes for Regulating Transformers, Mar. 16,1965 there are many different kinds of Jansen type transfer switchesinvolving different circuitries and different sequences of tap-changingswitching steps. Reference may be had to this patent for details inregard to the design and performance features of various kinds of Jansentype transfer switches. The transfer switch L of FIG. 1 is one of manytransfer switches which may be used jointly with selector switchesembodying the present invention. The transfer switch of FIG. 1 includesa cylindrical support 15 for fixed contacts 11, 12, 13, 14. Only aportion of support 15 has been shown in FIG. 1. Fixed contacts .11, 12are outer contacts, or main contacts, and fixed contacts 13, 14 areinner contacts, or auxiliary contacts. Reference characters 21 and 22have been applied to indicate a pair of movable main contacts, andreference characters 23 and 24 have been applied to indicate a pair ofmovable auxiliary contacts. Contacts 11 and 21 are adapted to be broughtinto engagement. and out of engagement by means of a link which supportscontact 21. In a like fashion contacts 13, 23; 14, 24 and 12, 22 may bebrought into and out of engagement by links which support movablecontacts 23, 24, 22. Reference character A has been applied in FIG. 1 toindicate an outgoing line to which all of the movable contacts 21, 22,23 and 24 are conductively connected. Fixed contacts 11 and 13 areinterconnected by a resistor R. In a like fashion fixed contacts 12 and14 are interconnected by a resistor R. The operation of contacts 21, 22,23 and 24 in the required sequence may be performed by linkage operatingmeans of the character described in considerable detail in US. Patent3,218,400 to A. Bleibtreu, May 16, 1965 for Transfer Switches forTap-Changing Regulating Transformers Having Squirrel-Cage-Shaped Supportfor the Fixed Contacts Thereof. It will be apparent from FIG. 1 that thefixed contacts and the movable contacts of the structure shown thereinare arranged in sector-like fashion, or encompass a space which is asector of a cylinder. In three-phase circuits the transfer switchincludes three such sector-like contact arrangements, each for one phaseof the three-phase circuit. Line A may then be connected to the neutralpoint of the transformer, assuming the latter to be star-connected.

The selector switch St includes a pair of stationary slip rings 31, 32of which the former is conductively connected by lead 25 to fixedcontact 11 of transfer switch L, and the latter is conductivelyconnected by lead 26 to fixed contact 12 of transfer switch L. Theselector switch St includes a relatively large number of fixed contacts1, 2, 3 Only three such contacts are shown in FIG. 2, and additionalfixed contacts including contacts 5, 6 are shown in FIG. 3. All oddnumbered contacts are arranged in a circular pattern on a relativelyhigh level and all even numbered contacts are arranged in a coaxialcircular pattern on a relatively lower level, as clearly shown in FIG.3. The contacts 1, 2, 3 of selector switch St are supported by a systemof vertical rods 33 of insulating material which form asquirrel-cake-like structure, as clearly shown in FIG. 3. Slip ring 31is arranged in a plane defined by odd numbered contacts 1, 3 and sliprings 32 is arranged in a plane defined by even numbered contacts 2, 4Slip rings 31, 32 are fixedly mounted on a column of insulating materialarranged along the axis of the cylindrical surface defined by rods 33.Reference character 40 has been applied to indicate the housing of agear mechanism for operating the selector switch St. The selector switchSt further includes an upper contact arm, or contact bridge 35, whoseradially outer end engages the odd numbered contacts 1, 3 and whoseradially inner end engages slip ring 32. The lower contact arm 36 ofselector switch St engages with the radially outer end thereof the evennumbered contacts 2, 4 and with the radially inner end thereof slip ring.32. Contact arms or contact bridges 35, 36 are adapted to be pivotedabout the axis of column 34, as will be shown below more in detail.Contact arm, or contact bridge 36, is provided with a sliding contact orbrush contact 37 which establishes a conductive connection betweencontact bridges 35, 36 when these contact bridges are in positions ofregistry.

The odd numbered contacts of the selector switch are conductivelyconnected with the odd numbered contacts of a tapped transformer winding(not shown), and the even numbered contacts of the selector switch areconductively connected with the even numbered contacts of that winding.Thus the following current path is established: tap 1 on a tappedtransformer winding (not shown), fixed contact 1 of selector switch St,contact bridge 35, slip ring 31, lead 25, main contacts 11, 21 oftransfer switch L and lead A. The contact bridge 36 does not carrycurrent at the time contact bridge 35 engages contact 1 and carriescurrent along the above current path 35, 25, 11, 21, A; 'but it isarranged at that time in registry wth contact bridge 35 and conductivelyconnected with contact bridge 35 by sliding contact or brush contact 37.As a result, the same potential is applied to fixed contact 12 oftransfer switch L as to the fixed contact 11 thereof. Because of thepresence of resistors R fixed contacts 13-, 14 are at the same potentialas contacts 11 and 12 which, as mentioned above, is the same by virtueof the particular design of selector switch St. On the other hand, allmovable contacts 21, 22, 23, 24 of transfer switch L are at the samepotential since they are conductively interconnected by lead A. Thus allcontacts of transfer switch St are at the same potential when thetransfer switch is either in its limit position shown in FIG. 1, or inits opposite limit position. In the latter movable main contact 22 is inengagement with fixed main contact 12, and all other contacts are out ofengagement. In either of the two aforementioned limit positions thecurrent flow through transfer switch L is stationary, transientconditions being limited to the short intervals of time when transferswitch L is moved between its two limit positions. As long as transferswitch L is in either of its two limit positions, and stationary circuitconditions prevail, all the contacts of transfer switch L are at thesame potential, i.e. the potential of the current-carrying contact ofselector switch St.

In three-phase transfer switches of the kind indicated in FIG. 1 a pairof closed main contacts of one phase is situated immediately adjacent apair of open main contacts of another phase. This makes it particularlydesirable to equalize voltages between main contacts in the fashionwhich has been outlined above.

Each switching step of contact bridges 35, 36 corresponds to one half ofthe circular pitch of fixed contacts 1, 3 and fixed contacts 3, 5respectively. This is a prerequisite of achieving the registry positionof contact bridges 35, 36 illustrated in FIG. 1. FIG. 2 illustrates thevery instant in which contact bridge 36 is moving out of its registryposition with contact bridge 35 into engagement with fixed contact 2 ofselector switch Sr, this being effected by a pivotal motion of contactbridge 36 in clockwise direction, as seen in FIG. 2. When contact bridge36 has engaged fixed contact 2 of selector switch St, transfer switch Lbecomes operative, and when its transfer operation is completed itscontacts 12 and 22 are in engagement, and all its other contacts out ofengagement. At this point of time tap 2 of the transformer winding (notshown) is conductively connected with lead A by the intermediary ofselector switch St and transfer switch -L. After contact bridge 36 hasengaged fixed contact 2 of selector switch St, the contact bridge 35' ofthe latter is moved one half circular contact pitch in clockwisedirection, as seen in FIG. 2, i.e. half the distance between fixedcontacts 1 and 3 of selector switch St. As a result, contact bridges 35and 36 are again in one of their registry positions and are againconductively interconnected by sliding contact or brush contacts 37.Hence all contacts of transfer switch L are again at the same potential,which is now that of tap 2 and fixed contact 2 of selector switch St. Itis thus apparent that differences in potential between the contacts oftransfer switch L pertaining to the same phase are limited to the shortperiods of time during which the selector switch and the transfer switchare being operated.

The Geneva gear drive illustrated in FIGS. 4 and 5 is one of thepossible means for achieving the required timing of the operations ofthe systems shown in FIGS. 1 and 2. The gear drive is arranged in ahousing 40 which is preferably arranged above the selector switch (seeFIG. 3). Geneva gears 41 and 42 are mounted on a common shaft 49 andarranged one above the other. Both Geneva gears 41, 42 are operated by acam gear 43 mounted on and driven by shaft 44. The upper surface of camgear 43 is provided with a cam 45 for engaging Geneva gear 41, and thelower surface of cam gear 43 is provided with a cam 46 for engagingGeneva gear 42. Verictal rod 47 is integral with Geneva gear 41 andprojects downwardly to operate, or pivot, contact bridge 35 cooperatingwith the odd numbered contacts of the selector switch St. In likefashion vertical rod 48 is integral with Geneva gear 42 and projectsdownwardly to operate, or pivot, contact bridge 36 cooperating with theeven numbered contacts of the selector switch St. Shaft 49 on whichGeneva gears 41 and 42 are mounted is, in turn, supported by gear box orhousing 40.

When transfer switch L is in one of its limit positions and the contactbridges 35, 36 of selector switch St in their registering positions,i.e. when both switches L and St are in one of their permanentpositions, as distinguished from their transient positions, Geneva gears41 and 42 are angularly displaced in such a fashion that the centerlines of the slots 411 of gear 41 are-in registry with the center linesof the wing portions 422 of Geneva gear 42. In that position of genevagears 41, 42 the center lines of slots 421 of Geneva gear 42 are inregistry with the center lines of the wing portions 412 of Geneva gear42. This is clearly apparent from FIG. 5. When cam gear 43 is pivoted incounterclockwise direction about a predetermined angle 06 as indicatedby an arrow in FIG. 5, cam 46 of gear 43 pivots Geneva gear 42 inclockwise direction, as seen in FIG. 5. As a result of this pivotalmotion of Geneva gear 42 the center lines of slots 421 of gear 42 andthe center lines of slots 411 of gear 41 are arranged in registry. Ascam gear 43 continues its pivotal motion in counterlockwise directionabout angle 6, the transfer switch is caused to operate as a result ofwhich its contacts are moved from the limit position shown in FIG. 1 tothe opposite limit position wherein its contacts 12 and 22 are inengagement, and all its other contacts are out of engagement. Thereuponcam 45 on cam wheel 43 engages slot 411 of Geneva gear 41 and pivotsabout the angle 'y. As a result, Geneva gear 41 is moved in such afashion that the center lines of its slots 411 are in registry with thecenter lines of wings 422 of Geneva gear 42. Now a tap-changingoperation, or a tapchanging duty cycle, has been completed and all partsof switches L and St are in rest position, another tap and anothercontact of switch L now carrying current than the tap and the contact ofswitch St carrying current at the beginning of the tap-changingoperation. In this position of rest Geneva gear 42 is locked by means oflocking device 452. In like fashion Geneva gear 41 had been locked inits initial position shown in FIG. 4 by locking device 461 on cam gear43. Locking devices 452 and 461 are integral with cam gear 43 and engagein the locking positions thereof corresponding recesses provided inwings or wing portions 412 and 422 of Geneva gears 41 and 42,respectively. Each cam 45 and 46, respectively, of cam gear 43 foroperating Geneva gears 41, 42 is provided with one of the aforementionedlocking devices 452 and 461 for locking the other Geneva gears 42 and 41in position.

As mentioned above, FIG. 6 is a diagrammatic representation of thesequence of steps involved in the operation of the structure of FIGS. 4and 5. The distances a and correspond to half the circular pitch stepsof the Geneva gears 41, 42 driving selector switch St of FIGS. 1 and 2.The distance or length 7 represents the angle of rotation of cam gear 43during which transfer switch L is moved from one of its limit positionsto the other limit position thereof. It is apparent from FIG. 6 that thefirst half circular pitch step of the Geneva gear drive by which one ofcontact bridges 35, 36 is operated is performed prior to the movement oftransfer switch L from one of its limit positions to the other, whilethe second half circular pitch step of the Geneva gear drive by whichthe other of the two contact bridges 35, 36 is operated is performedsubsequent to the movement of transfer switch L from one of its limitingpositions to the other.

The selector-switch-operating gear mechanism of FIGS. 7 and 8 includes apair of Geneva gears 51, 52 which are arranged in a common plane, and acam gear 53 which is arranged between the two aforementioned Genevagears. A driving shaft 54 operates a worm gear mechanism 54a and camgear 53 is mounted on the shaft 54b of the worm gear of worm gearmechanism 54a. Cam gear 53 is provided with a cam 55 which is adapted tocooperatively engage both Geneva gears 51, 52. Cam gear 55 is furtherprovided with a locking device 551 which is angularly displaced 180degrees relative to its cam 55. Selector-switch-operating rod 57 issecured to Geneva gear 51 and operates the contact bridge 35 forselecting odd numbered fixed contacts 1, 3 of selector switch St, andGeneva gear 52 is integral with selector-switch-operating rod 58 whichoperates contact bridge 36 for the even numbered fixed contacts 2, 4 ofselector switch St. Reference numeral 50 has been applied to indicate agear box or housing for the selector-switchoperating gear.

As shown in FIG. 8 both Geneva gears 51, 52 are arranged in such afashion that when its above gears are in the rest position thereof thecenter line of one of the slits 511 in gear 51 is juxtaposed to thecenter line of one of the wings 522 of gear 52. In this rest position ofthe Geneva gear drive both contact bridges 35, 36 of selector switch Stare in their rest positions wherein they are registering andconductively interconnected by slide contact or brush contact 37 andtransfer switch L is like wise in a position of rest, i.e. in one of thetwo limit positions thereof. Operation of the selector-switch-operatinggear is initiated by a pivotal motion of cam gear 53 in the direction ofthe arrow of FIG. 8, or in counterclockwise direction, about the angle0:. As a result, Geneva gear 52 moves contact bridge 36 by theintermediary of contact-bridge-operating shaft 58 say from fixed contact1 toward fixed contact 2. As cam gear 53 continues its pivotal motion incounterclockwise direction about the angle fi, it is out of meshingengagement with Geneva gear 52. As cam gear 53 moves along thetrajectory corresponding to angle 5, the transfer switch L is caused tooperate and to move from one of its limit positions to the other, e.g.from the limit position shown in FIG. 1 wherein its main contacts 11, 21are in engagement and conductively connected to the fixed contact 1 ofselector switch St to the limit position in which its main contacts 12,22 are in engagement and conductively connected to fixed contact 2 ofselector switch St. As cam gear 53 continues its pivotal or rotationalmotion along the trajectory which corresponds to angle 7, its cam 55 isin meshing engagement with Geneva gear 51. This causes a pivotal motionof Geneva gear 51 and of selector-switch-operating shaft 57 as a resultof which contact bridge 35 is being operated, e.g. moved to fixedcontact 2 of selector switch St and to a position of registry withcontact bridge 36. This completes a switch over duty cycle as, forinstance, switching from tap 1 and fixed contact 1 to tap 2 and fixedcontact 2.

FIG. 9 illustrating the sequential steps involved in the operation ofthe Geneva gear of FIGS. 7 and 8 is selfcxplanatory in view of theforegoing.

Referring now to FIGS 10 and 11, the selector-switchoperating gearmechanism shown therein includes a pair of cog wheels or pin wheels 61and 62 which are arranged side by side in a common plane. Cam gear 63 isarranged between cog wheels or cog gears 61, 62. Shaft 64 operates aworm gear 64a including a shaft 64b on which cam gear 63 is mounted. Camgear 63 includes a pair of cams 65 and 66 arranged to one side thereofand a locking device 651 arranged to the other side thereof. Cog wheel61 is provided with equidistant cogs 611 and operates a shaft 67 foroperating contact bridge 35 cooperating with the odd numbered fixedcontacts of selector switch St. Cog wheel 62 is provided withequidistant cogs 622 and operates a shaft 68 for operating contactbridge 36 cooperating with the even numbered fixed contacts of selectorswitch St. The cog-wheel-drive for operating contact bridges 35, 36 isarranged in a gear box or gear housing 60.

If cam gear 63 is pivoted about is shaft 64b in clockwise direction asseen in FIG. 10, cam '66 engages the cog 611 situated between earns 65and 66 and moves cog wheel 61 along the angle a. As a result, shaft 67moves contact bridge 35 one step. This corresponds to a pivotal motionof cam wheel 63 about the angle 06. As cam wheel 63 is further movedabout the angle ,8, both cog wheels 61, 62 stand still. In this intervalof time the transfer switch L is caused to switch to the fixed contactof selector switch L which has been pre-selected by the operation of cogwheel 61. The motion of deg. of cam wheel 63 is completed by movingalong the angle 7. During the last phase of the aforementioned pivotedmotion of cam wheel 63 its cam 65 pivots cog wheel 62 about the angle 7indicated in FIG. 10. As a result, shaft 68 of cog wheel 62 movescontact bridge 36 one step into registry with contact bridge 35, thusestablishing a conductive connection between both contact bridges 35,36.

FIG. 12 illustrates the above referred-to switching cycle and isself-explanatory.

The gear mechanism of FIGS. 4 and 5 is intended to operate directlycontact bridges 35, 36, i.e. merely by the intermediary of rods 47, 48which are integral with contact bridges 35, 36. The shafts 57, 58 of theGeneva gear of FIGS. 7 and 8 are intended to operate an intermediategear (not shown) which, in turn, operates contact bridges 35, 36. In thesame fashion the shafts 67, 68 of cog wheels 61, 62 of FIGS. 10 and 11are intended to operate an intermediate gear (not shown) which, in turn,operates contact bridges 35, 36.

Jansen type tap-changing regulating transformers are generally providedwith an operating head arranged above the transfer switch. Thetransferswitch is arranged above the selector switch and both thetransfer switch and the selector switch are operated by theaforementioned operating head. This has been indicated in the copendingpatent application of Ulrich G. E. Schweitzer, filed July 5, 1967, Ser.No. 651,284 for Tap-Charging Transformer Including a Selector Switch anda Transfer Switch. It is also shown in greater detail in the printedpublication titled Stufenschalter Typ D System Dr. Jansen published byMaschinenfabrik Reinhausen Gebriider Scheubeck KG., Regensburg, WestGermany (see particularly FIG. 11 which is self-explanatory). The Genevagear drive of FIGS. 4 and 5 is intended to be arranged immediately abovethe selector switch, i.e. between the transfer switch and the selectorswitch, shaft 44 of FIGS. 4 and 5 extending upward to the aforementionedoperating head and being driven by the same. The Geneva gear drive ofFIGS. 7 and 8 and the cog wheel drive of FIGS. 10 and 11 are integralparts of the aforementioned operating head. In other words, they areintended to be arranged at a higher level than the Geneva gear drive ofFIGS. 4 and 5. The shafts 57 and 58 of FIGS. 7 and 8 and the shafts 67and 68 of FIGS. 10 and 11 transmit the step motions of the gears shownin these figures to an intermediate gear (not shown) arranged betweenthe transfer switch and the se1ector switch which intermediate earoperates the contact bridges 35, 36 of the selector switch St. Thisintermediate gear may be a normal spur gear including a pair of wheelsarranged in coaxial relation to the selector switch St of which each isintegral with one of the contact bridges 35, 36. This may be achieved bymeans of vertical tie rods similar to the rods 47, 48 of FIG. 4. Theabove referred to Maschinenfabrik Reinhausen publication shows thepositioning of an intermediate gear and the way it is being operatedfrom the operating head of the regulating transformer. Theaforementioned US. Patent 3,250,864 refers to a regulating transformerincluding a Geneva gear drive which is arranged between the transferswitch and the selector switch and driven by a shaft 57 extendingupwardly to the operating head of the regulating transformer. The Genevagear drive of FIGS. 4 and 5 is intended to be positioned and operated inthe same fashion as the Geneva gear drive of US. Patent 3,250,864.

While, in accordance with the patent statutes, we have disclosed thespecific details of preferred embodiments of the invention, it is to beunderstood that these details are merely illustrative and that manyvariations thereof may be made without departing from the spirit andscope of the invention. It is, therefore, our desire that the languageof the accompanying claims be interpreted as broadly as possible, andthat it be limited only by the prior state of the art.

We claim as our invention:

1. In a selector switch for load tap-changers of regulating transformersthe combination of:

(a) a first plurality of fixed odd numbered contacts arranged in a firstcircular pattern defining a first plane, said first plurality of fixedcontacts having a predetermined circular contact pitch;

(b) a second plurality of fixed even numbered contacts arranged in asecond circular pattern coaxial with said first circular pattern anddefining a second plane spaced from and parallel to said first plane,said second plurality of fixed contacts having the same predeterminedcircular pitch as said first plurality of fixed contacts;

(0) a pair of fixed slip rings arranged in coaxial relation to saidfirst plurality of fixed contacts and to said second plurality of fixedcontacts, said pair of fixed slip rings including a first slip ring anda second slip (d) a pair of contact bridges pivotable about the commonaxis of said first plurality of fixed contacts and said second pluralityof fixed contacts, said pair of contact bridges including a firstcontact bridge and a second contact bridge, said first contact bridgehaving a radially inner end permanently engaging said first slip ringand having a radially outer end selectively engaging any of said firstplurality of fixed contacts, and said second contact bridge having aradially inner end permanently engaging said second slip ring and havinga radially outer end selectively engaging any of said second pluralityof fixed contacts;

(e) a pair of operating means for pivoting said first contact bridge andsaid second contact bridge about said common axis of said firstplurality of fixed contacts and said second plurality of fixed contact?in steps equal to half said circular contact pitch to cause saidradially outer end of said first contact bridge to engage consecutivecontacts of said first plurality of fixed contacts and to cause saidradially outer end of said second contact bridge to engage consecutivecontacts of said second plurality of fixed contacts upon having beenpivoted two said steps in the same direction; and

(f) additional contact means establishing a conductive connectionbetween said pair of contact bridges in registering positions of saidpair of contact bridges.

2. A selector switch as specified in claim 1 including asquirrel-cage-structure having supporting rods of insulating materialfor said first plurality of fixed contacts and for said second pluralityof fixed contacts.

3. A selector switch as specified in claim 1 including a sliding contactfixedly supported by and conductively connected to one of said pair ofcontact bridges and slidingly engaging the other of said pair of contactbridges in registering positions of said pair of contact bridges.

4. A selector switch as specified in claim 1 including a common drivefor said pair of operating means and means establishing a lost motionconnection between said common drive and said pair of operating means,said common drive being adapted to sequentially engage each of said pairof operating means and to be disengaged from both of said pairs ofoperating means in intervals of time following disengagement from one ofsaid pair of operating means and prior to engagement of the other ofsaid pair of operating means to establish a pausebetween each step ofone of said pair of operating means and a consecutive step of the otherof said pair of operating means.

5. A selector switch as specified in claim 1 including acommon-drive-operated rotatable cam means and a pair of gears eachoperable by said cam means, said cam means and said pair of gears beingshaped and arranged to cause sequential engagement by said cam meansduring a rotary degrees motion thereof of each of said pair of gears,and said cam means and said pair of gears being shaped and arranged toallow a predetermined travel of said cam means out of engagement withboth said pair of gears subsequent to disengagement of said cam meansfrom one of said pair of gears and prior to engagement of said pair ofcam means with the other of said pair of gears.

6. A selector switch as specified in claim 1 including a cam gear havinga pair of cams angularly displaced 180 degrees and a pair ofsuperimposed Geneva gears each for operating one of said pair of contactbridges and each operable by one of said pair of cams, said pair ofGeneva gears being normally angularly displaced so that the centers ofthe slots of one of said pair of Geneva gears register with the centersof the wings of the other of said pair of Geneva gears.

7. A selector switch as specified in claim 1, including a cam gearhaving on opposite sides thereof a pair of cams angularly displaced 180degrees, said selector switch further including a pair of superimposedGeneva gears each for operating one of said pair of contact bridges andeach operable by one of said pair of cams, said pair of Geneva gearsbeing normally angularly displaced so that the centers of the slots inone of said pair of Geneva gears register with the centers of the wingsof the other of said pair of Geneva gears, and said cam gear having anopposite sides thereof a pair of locking devices angularly displaced 180degrees each adapted to enter the slots in one of said pair of Genevagears.

8. A selector switch as specified in claim 1 including a pair of Genevagears each for operating one of said pair of contact bridges, said pairof Geneva gears being arranged substantially in a common plane andhaving spaced centers, a cam arm pivotable about a shaft arranged atright angles to said common plane between said centers of said pair ofGeneva gears, said cam arm having a cam means arranged to sequentiallyengage said pair of Geneva gears and said pair of Geneva gears beingnormally angularly displaced in such a fashion that the centers of theslots in one of said pair of Geneva gears are juxtaposed to the centersof the wings in the other of said pair of Geneva gears.

'9. A selector switch as specified in claim 1 including a pair of Genevagears each for operating one of said pair of contact bridges, said pairof Geneva gears being arranged substantially in a common plane andhaving spaced centers, a cam arm pivotable about a shaft arranged atright angles to said common plane between said centers of said pair ofGeneva gears, said cam arm having a cam means arranged to engagesequentially said pair of Geneva gears when pivoted about an angle of180 degrees, said pair of Geneva gears being normally angularlydisplaced in such a fashion that the centers of the slots in one of saidpair of Geneva gears are juxtaposed to the centers of the wings of theother of said pair of Geneva gears, said cam arm further having alocking device angularly displaced 180 degrees relative to said cammeans thereof, and said locking device being shaped to conform with andto engage the radially outer edges of the wings of said pair of Genevagears.

10. A selector switch as specified in claim 1 including a pair of spacedcog wheels each for operating one of said pair of contact bridges and acam gear arranged between said pair of cog wheels and having a pair offork-shaped cam projections cooperatively engaging and alternatinglydriving one of said pair of cog wheels, said cam gear having acurve-shaped locking device angularly displaced 180 References CitedUNITED STATES PATENTS 3/1965 Bleibtreu et al. 200-l8 1/1941 St. Palley323-435 ROBERT K. SCHAEFER, Primary Examiner.

M. GINSBURG, Assistant Examiner.

US. Cl. X.R. 32343.5

